The present invention relates to a sheet guide apparatus which is used by a transfer cylinder or the like in a sheet-fed offset rotary printing press to regulate fluttering or the like of a sheet.
In a sheet guide apparatus in a sheet-fed offset rotary printing press, when a sheet to be conveyed by rotation of a transfer cylinder serving as a transport cylinder is thin, the trailing edge of the sheet flutters during conveyance due to low rigidity of the sheet. When the sheet is thick, the trailing edge of the sheet is separated from the transfer cylinder by the centrifugal force acting on the sheet under conveyance to come into contact with a sheet guide.
As shown in Japanese Patent Laid-Open No. 10-109404, a conventional sheet guide apparatus comprises an air duct which comes close to the outer surface of a transfer cylinder to serve as a sheet guide, and an air discharge nozzle which is arranged on the upper-side surface of the air duct to discharge air from a portion corresponding to the center of a sheet under conveyance toward two sides in the widthwise direction of the sheet. In this arrangement, air discharged from the air discharge nozzle forms an air flow layer between the upper-side surface of the air duct and the sheet under conveyance so as to convey the sheet with its trailing edge being in a stable state.
The conventional sheet guide apparatus described above requires a driving source which drives a fan to supply air to be discharged from the air discharge nozzle, leading to a high manufacturing cost. A driving system is also required to make the structure complicated. An installation space to install the driving source and an air supply system is also required to make the apparatus bulky.